Grade 7
  1. Introduction to Chemistry  1.1. What is Chemistry?  1.2. Importance of chemistry in daily life  1.3. Branches of chemistry  1.4. Scientific Method in Chemistry  1.5. Laboratory Safety Rules and Precautions  1.6. Common Laboratory Equipment and Their Uses  1.7. Units of measurement in chemistry
  2. Matter and its properties  2.1. Definition of Matter  2.2. Classification of matter  2.3. Properties of matter  2.3.1. Physical properties  2.3.2. Chemical properties  2.4. States of matter  2.4.1. Solid state  2.4.2. Fluid state  2.4.3. Gaseous state  2.4.4. Plasma and Bose–Einstein condensates  2.5. Changes in the states of matter  2.5.1. Melting and freezing  2.5.2. Evaporation and Condensation  2.5.3. Sublimation and deposition  2.6. Density and its applications  2.7. Diffusion and its importance
  3. Elements, Compounds, and Mixtures  3.1. Definition of the element  3.2. Classification of elements  3.3. Metals, Nonmetals and Metalloids  3.4. Noble gases and their properties  3.5. Introduction to the Periodic Table  3.6. Definition of Compound  3.7. Properties of Compounds  3.8. Introduction to Chemical Formulas  3.9. Definition of Mixture  3.10. Types of mixtures  3.10.1. Homogeneous mixture  3.10.2. Heterogeneous mixtures  3.11. Difference Between Compounds and Mixtures  3.12. Solutions, Colloids and Suspensions
  4. Separation of mixtures  4.1. Need for separation of mixtures  4.2. Separation methods  4.2.1. Filtration  4.2.2. Sedimentation and decantation  4.2.3. Evaporation  4.2.4. Crystallization  4.2.5. Distillation  4.2.6. Chromatography  4.2.7. Magnetic Separation  4.2.8. Centrifugation
  5. Atomic Structure  5.1. Introduction to Atoms  5.2. Structure of the atom  5.2.1. Nucleus and electron cloud  5.3. Subatomic particles  5.3.1. Proton  5.3.2. Neutron  5.3.3. Electrons  5.4. Atomic number and mass number  5.5. Isotopes and their uses  5.6. Ions and ion formation
  6. Periodic table  6.1. Introduction to the Periodic Table  6.2. Groups and periods  6.3. Trends in the Periodic Table  6.3.1. Atomic Size  6.3.2. Metallic and non-metallic character  6.3.3. Electronegativity  6.3.4. Reactivity of the elements  6.4. Alkali metals and their properties
  7. Chemical bond  7.1. Why do atoms form bonds?  7.2. Types of chemical bonds  7.2.1. Ionic bond  7.2.2. Covalent bond  7.2.3. Metal Bond  7.3. Properties of Ionic and Covalent Compounds  7.4. Intermolecular forces
  8. Chemical reactions  8.1. Introduction to Chemical Reactions  8.2. Signs of a chemical reaction  8.3. Types of Chemical Reactions  8.3.1. Combination Reactions  8.3.2. Decomposition reactions  8.3.3. Displacement reactions  8.3.4. Double displacement reactions  8.3.5. Combustion reactions  8.4. Law of conservation of mass  8.5. Balancing simple chemical equations
  9. Acids, Bases and Salts  9.1. Definition of Acid and Base  9.2. Properties of Acids  9.3. Properties of bases  9.4. pH Scale and Indicators  9.5. Neutralization reactions  9.6. Common Acids and Bases in Everyday Life  9.7. Preparation and use of salts  9.8. Strong and weak acids and bases
  10. Solutions and Solubility  10.1. Definition of Solution  10.2. Components of the solution  10.2.1. Solvent  10.2.2. solute  10.3. Factors Affecting Solubility  10.4. Concentration of solutions  10.5. Saturated and unsaturated solutions  10.6. Colloids and suspensions  10.7. Solubility curve and its interpretation
  11. Air and atmosphere  11.1. Composition of air  11.2. Properties of gases in the air  11.3. Importance of Oxygen and Carbon Dioxide  11.4. Air pollution and its effects  11.5. Greenhouse effect and global warming  11.6. Ways to reduce air pollution  11.7. Ozone layer and its importance
  12. Water and its importance  12.1. Properties of Water  12.2. Water as the universal solvent  12.3. Importance of water for life  12.4. Water pollution and its effects  12.5. Water Purification  12.5.1. Filtration  12.5.2. boil  12.5.3. Chlorination in water purification  12.5.4. reverse osmosis  12.6. Hard and soft water  12.7. Water cycle and its importance
  13. Fuel and energy  13.1. Types of fuel  13.1.1. Fossil fuels  13.1.2. Renewable energy sources  13.2. Combustion and energy release  13.3. Global warming and its effects  13.4. Alternative sources of energy  13.5. Ways to conserve energy
  14. Metals and Nonmetals  14.1. Physical and chemical properties of metals  14.2. Physical and Chemical Properties of Non-Metals  14.3. Difference Between Metals and Nonmetals  14.4. Uses of metals and nonmetals  14.5. Corrosion of metals and its prevention  14.6. Alloys and their importance
  15. Plastics and polymers  15.1. Natural and synthetic polymers  15.2. Properties of plastics  15.3. Biodegradable and Non-Biodegradable Plastics  15.4. Environmental impact of plastic  15.5. Recycling and waste management in plastics and polymers  15.6. Daily Uses of Polymers
  16. Introduction to Organic Chemistry  16.1. Basic definitions of organic chemistry  16.2. Carbon Compounds in Daily Life  16.3. Hydrocarbons  16.4. Simple functional groups (alcohols and carboxylic acids)  16.5. Importance of organic compounds in industry

Grade 7 → Water and its importance ↓


Water pollution and its effects


Introduction to water and its importance

Water is a vital substance on Earth. It is essential for all forms of life, from plants and animals to humans. About 71% of the Earth's surface is covered by water, mostly in the form of oceans. However, not all water is usable for drinking. Freshwater, which accounts for only 2.5% of the total water on Earth, is what humans depend on for most of their activities, including drinking, cooking, farming, and cleaning.

The chemical formula for water is H 2 O, which means that each water molecule is made up of two hydrogen atoms and one oxygen atom. These chemical properties make water an excellent solvent, which means that it can dissolve many substances.

Water (H₂O)
,
|HOH |
,

Understanding water pollution

Water pollution occurs when harmful substances contaminate water bodies such as rivers, lakes, streams, oceans, and groundwater. This can make the water unsuitable for drinking and other essential uses. Polluted water affects plants, animals, and humans. It is primarily caused by human activities, although natural occurrences can also cause pollution.

Let us consider a simple example. Imagine a glass of clear water. If you add a spoonful of mud to it, the water becomes cloudy. Now think of adding chemicals instead of mud. This is similar to what happens in natural water bodies when there is pollution.

Sources of water pollution

1. Industrial waste

Industries are one of the major sources of water pollution. Factories often discharge dirty water containing chemicals into rivers and lakes. These chemicals can be toxic and harm aquatic life, plants and humans that depend on polluted water.

2. Agricultural runoff

Agriculture uses fertilizers and pesticides that can flow into nearby water bodies when it rains. These substances can cause algae growth, which consumes a lot of oxygen, affecting the survival of other aquatic life.

3. Household waste

Everyday waste from households, such as cleaning agents and personal care products, can end up in water systems. These contain a variety of chemicals that cannot be completely removed by wastewater treatment plants.

4. Oil spill

Oil spills are the release of petroleum into the ocean or coastal waters. They spread rapidly across the water's surface, harming marine life and habitats.

Visual example of water movement

river or stream

Effects of water pollution

1. Harm to aquatic life

Water pollution can greatly affect aquatic life. Pollutants such as chemicals and plastics can harm the health of fish, plants, and other animals living in water bodies. For example, when oxygen levels are reduced due to pollution, aquatic animals cannot survive.

2. Health problems in humans

Contaminated water can cause serious health problems for humans, including cholera, dysentery, and other gastrointestinal problems. This is especially true in areas where access to clean drinking water is limited.

3. Disruption of the ecosystem

Pollution can alter the natural balance of an ecosystem. Poor water quality can cause some species to die, which can lead to changes in the entire ecosystem. This also affects animals and plants that depend on the affected species for food or shelter.

Preventing water pollution

1. Proper waste disposal

Ensuring proper disposal of household chemicals, oils and non-biodegradable items can help prevent them from entering water systems. This includes using recycling facilities and hazardous waste disposal centers where possible.

2. Sustainable agriculture

By adopting sustainable agricultural practices, such as using organic fertilizers and creating buffer zones to filter runoff, water pollution from farms can be greatly reduced.

3. Industrial regulation

Governments can impose strict regulations on industrial waste disposal to ensure that waste is treated before being released into the environment.

4. Public awareness

Educating the public about the causes and effects of water pollution can encourage more environmentally responsible behavior.

Visual example of the effects of pollution

Oil spill polluted water

Conclusion

Water pollution is a serious issue that affects everyone and everything that depends on clean water. By understanding its sources, effects, and methods of prevention, we can work toward reducing pollution and protecting this precious resource. Clean water is essential to our survival, and each of us must play a role in keeping it safe and pure for future generations.


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